Relay construction



March 11, 1958 L. K. RAFTREE 2,826,659

RELAY CONSTRUCTION Filed Sept. 7, 1956 IN V EN TOR.

United States Patent 6 RELAY CQNSTRUCTION Leonard K. Raftree, Elkhart, -Ind., assignor to Durakool, Inc, Elkhart, Ind., a corporation of Indiana Application September 7, 1956, Serial No. 608,526

6 Claims. (Cl. 200-112) My present invention relates to improvements in electrical relays and particularly mercury contact relays.

The features of the present invention are especially adapted for displacer type mercuryrelays of both the normally closed and normally open classes. In the particular embodiment of my invention herein disclosed, I have shown the same in association with a displacer type mercury to mercury contact relay of the normally open class, although its utility with other classes of mercury relays or other relay mechanisms will be readily appreciated by those familiar in the art. Briefly, my present invention pertains especially to mercury relays having plunger means adapted for movement within a casing for making and breaking electrical circuit through the-relay. In the class of relay herein illustrated, it is common practice to embody an outer metal casing or shell which serves as one electrode or circuit terminal. The outer metal casing supports a body of mercury within its lower end and a plunger means is adapted to have normal fioating relation in such body of mercury. An electro-magnetic coil surrounds the outer metal shell and upon energization causes the plunger to immerse or sink into the body of mercuryand displace the same upwardly whereat such closes contact between the casing and a second electrode disposed substantially coaxially of the outer casing and insulated therefrom.

Movement of the plunger within the outer metal casing without frictional engagement therewith would be ideal in devices as aforementioned. Thus, if a purely concentric relation could be maintained between the plunger and the outer metal casing, then the only frictional resistance to its movement axially of the casing occurs through its contact with the body of mercury. However, in the normal operation of such a plunger, energization of the electro-magnetic coil results in a slight cocking of the plunger to bring the same in contact with the side walls of the outer metal casing. Various expedients have been employed in the past to minimize such frictional engagement between the plunger and the interior side walls of the outer metal casing as, for example, by providing a plurality of encircling rows of ball bearings protruding from the exterior of the plunger body, usually of the opposite ends thereof, for rolling contact with the inside face of the outer metal casing. A similar expedient embodies encircling rows of protrusions or semi-spherical projections formed in the walls of the plunger body for engaging the walls of the casing with substantially point contact. In resorting to such expedients previous to the present'invention, the ball bearings or protrusions of the encircling rows have further been aligned in rows parallel to the longitudinal axis of the plunger, thereby providing point engagement between opposite ends of the plunger and the interior walls of the outer metal casing.

My present invention seeks to improve upon the use and arrangement of such friction reducing means by substantially reducing the overall frictional resistance to movement of the plunger. vention seeks to substantially reduce such frictional en- Briefly, in this regard, my in 2,826,659 PatentedMar; 11,- 1958 gagement by establishing a three point engagement arrangement between such plunger and 'its'surrounding mercury containing outer metal-casing through the alignment of such points of engagement to minimize the number thereof which make contact with the casing at any one time.

The main object of this invention is to provide a new and improved construction for plungers' utilized in mercury type relays.

Another object of my invention is to provide a new and improved means for reducingfrictional engagement between the plunger member of a mercury type relay and an outer metal casing containing a body of mercury in which such plunger operates.

A still further object of my invention is to provide a new and improved means requiring the protrusion of point engaging members between the plunger and an outer metal casing in a mercury type relay with such point engaging members being arranged to give the plunger stability of movement while limiting their engagement with the casing to three points-of contact.

The above and further objects features and advantages of this invention will become apparent to those familiar with the art from the following detailed description and specification of a preferred form of relay embodying my present invention as seen in the accompanying drawings.

In the drawings:

Figure 1 is an elevational view with parts therein broken away in cross-sectionshowing a typical normally open type mercury to mercuryrelay-structure embodying the concepts and features of my invention;

Figure 2 is a cross-sectional showingtaken substantially at line 2, 2 of Figure 1;

Figure -3 is an enlarged partial cross-sectional view taken throughone of the protrusions employed in my present invention, substantially as viewed from line 3, 3 of Figure l; and

Figure 4 is a developed view of the shell employed in the construction of the plunger as set forth in Figure l to illustrate the unique arrangement and disposition of the point contact protrusions of the improved mercury relay plunger of this invention.

Turning now to the features of the device illustrated in the drawings, it will be seen in Figure 1 that 'a mercury to mercury contact type relay of a normally opened class is illustrated and indicated generally by numeral 10 therein. Such relay includes a cylindrical'outer metal cylinder 11 which is referred to as anouter metal casing hereinafter. This casing constitutes a first electrode for the relay; the same having connection with a typical circuit as by lead conductor 12. The casing 11 supports a body of mercury 13 in its lower end; it being understood that the casing 11 is suitably closed at its opposite ends according to conventional practice.

A plunger assembly 15 comprising an outer sleeve of magnetic metal is supported for axial movement within casing 11 by the body of mercury 13. A second electrode 16 depends axially from the upper end of the casing 11 for reception within the axial confines of a ceramic member 17 comprising an internal portion of the plunger 15. Circuit connection with electrode 16 is by lead conductor 18.

The outer metal casing is surrounded by a suitable insulator sleeve 19 which is sealed over at its ends as by seals 20. The entire assembly comprising the plunger 15, the outer metal casing 11 and the insulator sleeve 19 are suitably assembled coaxially of a conventional electro-magnetic coil 21 supported by bracket means 22 and joined electrically to a suitable source of electrical potential.

It will be understood that in a relay of the class shown in Figure 1, the plunger assembly 15 normally floats in the body of mercury 13 with an additional body of mercury 23 being contained within the interior of the ceramic 17 surrounding the second electrode 16. Upon energization of coil 21, plunger 15 is depressed into the main body of mercury 13 causing the same to rise between the plunger and interior side walls of the casing 11 to overflow the upper end of ceramic 17 and thereby mingle with the secondary body of mercury 23 to close circuit between the first electrode or casing 11 and the second electrode 16. As mentioned earlier, the vertical or axial movement of the plunger assembly 15 within the shell casing 11 is desirably as friction free as possible. Since it is necessary that a passageway means be provided between the exterior of the plunger assembly 15 and the interior of the outer metal shell 11, it will be understood that energization of the coil 21 can readily cause the plunger to cockor move laterally slightly thereby to engage the interior side walls of the metal casing 11. In order to decrease frictional engagement between the plunger assembly and the side walls of the outer metal shell 11, I have devised the improvement of the present invention as will now be set forth.

From Figure 1, it will be understood that the plunger assembly 15 comprises or includes an exterior metal shell .or casing 25 of substantially cylindrical configuration plification of such a plunger and valve means, typical for use in this situation may be found in United States Patent No. 2,658,124, issued to Glen L. Weimer on November 3, 1953. Other arrangements for slow make and quick break constructions may also be employed illepending on the desired end characteristics of the reay. i

From examination of Figures 2, 3 and 4, it will be understood that the shell 25 of the plunger assembly is formed with upper and lower encircling rows of uniformly radially projecting protrusions 30 and 36', each comprising a substantially semi-spherical outer surface. In the particular embodiment illustrated herein, ten such protrusions, five in each encircling row, are formed in the side walls of the shell 25 adjacent the-upper and lower ends thereof. While it is not new in the art to provide protrusions of this character in a relay plunger body, previous practice has been 'to circumferentially space the several protrusions so that one each of the protrusions 30 of the upper encircling row would lie in alignment longitudinally of the plunger with one each of the protrusions 30' of the lower encircling row. It will be seen, however, from examination of Figure 4, that the protrusion members 30 are not in alignment with protrusions 30'. On the contrary, the lower encircling row of protrusions 30 is circumferentially ofiset with respect to the upper protrusions '30 so as to provide, when the plunger is not in true coaxial relation in the casing, three points of contact with the inner surface of the casing 11. For example, when two adjacent protrusions 30 in the uppermost row on the plunger body 25 and a single intermediately disposed protrusion 30' of the lower encircling row thereof engages the inner surface of casing 11 they will contact the latter at points a, b and c, defining a triangulated contact arrangement, as diagramed in the developed view of Figure 4. This triangle relationship holds true for the entire peripheryof the cylindrical plunger body 25, since the protrusions in the upper row'lie circumferentially intermediate an adjacent pair of protrusions of the lower row, and vice versa, as will be reco nized best by examining Figures 2 and 4 of. the drawings. Stated in another way, it may be said that the pro trusions 30 in the upper encircling row are circumferentially offset with respect to the protrusions 30' in the lower encircling row. Bearing this relationship in mind, it will be understood that upon energization of coil 21 ensuing engagement between the plunger assembly 15 and the interior side walls of the metal casing 11 will establish contact at only three points or protrusions at any one instant; two at one end of the plunger and one at the opposite end thereof. This triangle of contact also gives stability to the plunger during its axial movement within the casing 11. If it be considered that the plunger is cocked slightly clockwise or counter-clockwise from its Figure 1 position of concentricity with casing 11, then two of the uppermost protrusions 30 would engage the interior side walls of casing 11 while a single protrusion 30' disposed substantially diametrically opposite the two engaged protrusions 30 would establish the specified three points of contactbetween the plunger assembly and the outer metal casing. If pure lateral translation of th plunger occurs upon energization cede-energization of -coil 21, as the case may occur, then triangular contact on one side of the plunger body, such as illustrated in Figure 4 at points a, b and 0, would ensue; points a and b contacting the side walls of casing 11 adjacent the upper end of plunger assembly 15 and point 0 engaging such shell ;or casing adjacent the lower end plunger assembly 15. Conversely, if two points 30 engage the shell adjacent the lower end of the plunger then a single point of contact or'protrusionSt) at the upper end thereof will be involved. V V

. It will be understood that this offsetting relation between the upper and lower rows of protrusions on the plunger housing 25 results in a marked reduction of frictional engagement over previous plungers of this class embodying protrusions, ball bearing or other point contact friction reducing means in which the rows of such friction reducing means are disposed withthe members thereof in vertical registering alignment. Thus, for example, in the situation of previously known devices where two rows of protrusions similar to those illustrated in the accompanying drawings were provided, but with the members thereof in vertical or registering alignment, the normal case of lateral translation of the plunger assembly within the casing 11 would establish point contact at at least four of the friction reducing means or protrusion members. By employing my present modification of such previous structure, only three such protrusion members are involved. By thus eliminating one point of contact a 25% reduction in frictional engagement between the plunger and casing'is achieved.

While I have herein shown and described the features and concepts of my invention in relation to a preferred form of mercury relay, it is nevertheless to be understood and recognized that numerous changes, modification and substitutions of equivalents may be resorted to therein Without necessarily departing from the spirit and scope of its invention. As a consequence, it is not my intention to be limited to the particular form of device herein shown and described except as may appear in the following appended claims.

I claim:

l. A plunger for a mercury relay or the like, comprising a sleeve, a plurality of axially spaced encircling rows of spaced protrusions projecting uniformly radially outwardly of said sleeve, and the protrusions in one of said encircling rows being misaligned circumferentially of said sleeve relative to the protrusions in another of said encircling rows.

2. A plunger assembly for a mercury relay or the like,

' comprising a cylindrical sleeve of magnetic metal, a pair said encircling rows being spaced evenly with respect to each other, and the protrusions in one of said encircling rows being offset circumferentially relative to the protrusions in the other of said encircling rows.

4. A plunger for a mercury relay, comprising a cylindrical sleeve of magnetic metal, a pair of encircling rows of equally spaced apart protrusions, one row adjacent each end of the sleeve formed by displacing portions of said sleeve radially outward, said encircling rows having the same number of protrusions therein, all of which project uniformly radially outwardly of said sleeve, and

the protrusions in one of said encircling rows being circumferentially ofliset with respect to the protrusions in the other encircling row, whereby the protrusions in said encircling rows lie successively in alternate planes extending radially outwardly from the longitudinal axis of said Q sleeve.

5. A plunger for a mercury relay, comprising a cylindrical sleeve of magnetic metal, a plurality of axially spaced encircling rows of protrusions projecting uniformly radially outwardly of the outer periphery of said sleeve, the protrusions of one encircling row lying on lines parallet with the longitudinal axis of said sleeve, and the protrusions of the other encircling row lying on lines parallel with the longitudinal axis of said sleeve and intermediate the parallel lines on which the protrusions of said one row lie.

6. A mercury relay comprising a hollow casing having an internal cylindrical surface of substantially uniform diameter, a plunger disposed for movement in said casing and comprising a sleeve having its longitudinal axis extending lengthwise of the longitudinal axis of the internal cylindrical surface of said casing, said sleeve having encircling rows of the same number of protrusions adjacent each end thereof, said protrusions projecting uniformly radially outwardly of said sleeve to an extent in which the outer ends thereof define a cylindrical plane of a diameter slightly less than the diameter of the internal surface of said casing, and the protrusions in one of said encircling rows being offset relative to the protrusions in the other of said rows circumferentially of said sleeve, whereby upon longitudinal movement of said plunger in said casing in non-coaxial relation therewith, only one of the protrusions in one of said encircling rows and a pair of adjacent protrusions in the other encircling row frictionally engage with the internal cylindrical surface of said casing at any one time.

References Cited in the file of this patent 2,060,812 Gehrand et a1 Nov. 17, 1936 Larson Nov. 17, 1936' 

